1,720,974 research outputs found
Raman scattering from plasma excitations in a conducting double layer
No full textWe have investigated the Raman-scattering amplitude from processes in which the radiation field excites longitudinal collective modes in a system comprised of two parallel quasi-two-dimensional conducting electronic layers embedded in a dielectric medium. Within the random-phase approximation we have derived explicit formulas for the density response and the Raman intensity as a function of the exchanged frequency. The Raman spectrum consists of two resonance peaks corresponding to the optical- and acoustic-plasmon branches which are peculiar to this system. Both the position and the width of the resonances have been studied and are shown to depend on the electronic elastic lifetime
Frequency dependence of the electron self-energy in a two-dimensional electron liquid
No full textWe have studied the effects of the electron-electron interaction on the frequency dependence of the quasiparticle self-energy of a two-dimensional electron gas. Our approach is patterned after Hedin's GW approximation. We find that many-body effects associated with charge and spin fluctuations induced vertex corrections are important and cannot be neglected. For the sake of illustration the calculations have been carried out at zero temperature and taking advantage of the plasma-pole scheme. The validity of the familiar on-shell approximation is discussed
Perturbation theory of the Anderson model
No full textWe report the results of a systematic study of the single impurity Anderson model based on a perturbative approach. Our work provides new and exact results for a number of quantities of interest. In particular we have investigated the impurity spin susceptibility as well as the spatial dependence of the spin correlation density. In view of the versatility of the technique our calculations have been carried out for several specific models of the conduction electron bare density of states ρ0(ω). Both dynamical as well as thermodynamical properties have been investigated. Our results are compared with the ones obtained by means of the renormalization group analysis and recent quantum Monte Carlo studies. The breakdown of the Clogston-Anderson compensation theorem for realistic choices of ρ0(ω) is pointed out and discussed
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
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